The present disclosure relates to systems and methods for treating subterranean formations. More particularly, the present disclosure relates to systems and methods for wellbore pressure control with separated fluid columns.
In underbalanced and managed pressure drilling and completion operations, it is often beneficial to be able to maintain precise control over pressures and fluids exposed to drilled-through formations and zones. In the past, specialized equipment (such as downhole deployment valves, snubbing units, etc.) have been utilized to provide for pressure control in certain situations (such as, when tripping pipe, running casing or liner, wireline logging, installing completions, etc.) However, this specialized equipment (like most forms of equipment) is subject to failure, can be time-consuming and expensive to install and operate, and may not be effective in certain operations. For example, downhole deployment valves have been known to leak and snubbing units are ineffective to seal about slotted liners.
In addition to (or in lieu of) the specialized equipment, other approaches have involved the use of thixotropic fluids to form a barrier pill. As used herein, the term “barrier pill” refers to a batch of fluid and/or gel that is introduced into a wellbore to keep two other fluid layers substantially separate. For example, a barrier pill may be used to maintain a column of a low density fluid below a column of a high density fluid. If the barrier pill was not introduced, the higher density fluid would sink to the bottom of the wellbore. However, the materials used in barrier pills often lack sufficient strength or are prone to degradation in wellbore conditions.
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.